There are many occasions, particularly in industrial robotics and machining operations, when it is desired to provide movement of an object linearly and/or rotationally. Movement within a single plane, along an x and y axis, poses little problem. However, movement in the remaining two degrees of freedom, namely along a z axis and rotation about this axis, is more difficult to provide.
At present, a number of mechanisms are known for providing linear or rotational movement. These include mechanisms providing a screw for linear movement and a shaft actuated by a gear train for rotational movement, and mechanisms including a motor actuating an elongate rack for linear movement and a second motor to produce rotation. Alternatively, the entire apparatus which is to perform the operation can be moved linearly or rotated.
These mechanisms suffer from the fact that they are heavy and cumbersome, as well as being costly to manufacture. Their size and weight are particularly disadvantageous in applications where high speed motion is required or desired.